EP1564872A2 - Magnetkreise für elektrische Maschinen - Google Patents

Magnetkreise für elektrische Maschinen Download PDF

Info

Publication number
EP1564872A2
EP1564872A2 EP05250787A EP05250787A EP1564872A2 EP 1564872 A2 EP1564872 A2 EP 1564872A2 EP 05250787 A EP05250787 A EP 05250787A EP 05250787 A EP05250787 A EP 05250787A EP 1564872 A2 EP1564872 A2 EP 1564872A2
Authority
EP
European Patent Office
Prior art keywords
stator
flux
flux plate
rotor
plate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05250787A
Other languages
English (en)
French (fr)
Inventor
Michael Leo Mcclelland
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nidec SR Drives Ltd
Original Assignee
Switched Reluctance Drives Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Switched Reluctance Drives Ltd filed Critical Switched Reluctance Drives Ltd
Publication of EP1564872A2 publication Critical patent/EP1564872A2/de
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K19/00—Synchronous motors or generators
    • H02K19/02—Synchronous motors
    • H02K19/10—Synchronous motors for multi-phase current
    • H02K19/103—Motors having windings on the stator and a variable reluctance soft-iron rotor without windings
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/12—Stationary parts of the magnetic circuit
    • H02K1/14—Stator cores with salient poles
    • H02K1/146—Stator cores with salient poles consisting of a generally annular yoke with salient poles
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/18—Windings for salient poles

Definitions

  • This invention relates to improvements in the magnetic circuits of electrical machines. It is particularly suitable for those machines with salient poles, for example, switched reluctance machines.
  • a typical prior art switched reluctance drive is shown schematically in Figure 1.
  • This includes a DC power supply 11 that can be either a battery or rectified and filtered AC mains.
  • the DC voltage provided by the power supply 11 is switched across phase windings 16 of the motor 12 by a power converter 13 under the control of the electronic control unit 14.
  • the rotor and stator are typically radially laminated magnetisable steel, i.e. the plane of the laminations is radial with respect to the axis of the machine.
  • some machines are made up of axial laminations in which the plane of each lamination is parallel with the axis of the machine.
  • FIG. 2 One of the many known converter topologies is shown in Figure 2, in which the phase winding 16 of the machine is connected in series with two switching devices 21 and 22 across the busbars 26 and 27. Busbars 26 and 27 are collectively described as the "DC link” of the converter. Energy recovery diodes 23 and 24 are connected to the winding to allow the winding current to flow back to the DC link when the switches 21 and 22 are opened.
  • a capacitor 25, known as the “DC link capacitor” is connected across the DC link to source or sink any alternating component of the DC link current (i.e. the so-called “ripple current") which cannot be drawn from or returned to the supply.
  • the capacitor 25 may comprise several capacitors connected in series and/or parallel and, where parallel connection is used, some of the elements may be distributed throughout the converter.
  • a resistor 28 is connected in series with the lower switch 22 to provide a current feedback signal.
  • a multiphase system typically uses several "phase legs" of Figure 2 connected in parallel to energise the phases of the electrical machine.
  • Detection of rotor position is conventionally achieved by using a transducer 15, shown schematically in Figure 1, such as a rotating toothed disk mounted on the machine rotor, which co-operates with an optical, magnetic or other sensor mounted on the stator.
  • a signal e.g. a pulse train, indicative of rotor position relative to the stator is generated by the sensor and supplied to control circuitry, allowing accurate phase energisation.
  • a characteristic of some electrical machines is that they have salient poles on at least one member.
  • the stator lamination 40 and rotor lamination 45 shown in Figure 3 are suitable for a switched reluctance machine.
  • the stator lamination has salient poles 44.
  • a quantity of identical stator laminations make up the stator core 42.
  • the coils 49 are assembled to the stator core, either by sliding pre-wound coils onto the poles or by winding the coils directly onto the poles. In the assembled state the winding extends along each pole side (perpendicular to the plane of section A-A in Figure 3) and around each pole end between the sides.
  • the coils typically have an overhang portion 46 outside the core where the conductors bend in at least one plane around the pole end to connect the two coil sides together. Because of the constraints on minimum bending radius of conductors, there is usually a gap 47 between the inside of the coil overhang and the core at the pole end.
  • the rotor lamination also has salient poles 41, but these are typically not wound.
  • the identical rotor laminations are stacked to form a core pack and generally mounted on a shaft 48 which is mounted in bearings (not shown).
  • the rotor core pack is typically the same length as the stator core pack within manufacturing tolerances.
  • Electrical machines in general are constructed from laminations of magnetisable electrical sheet steel.
  • the resulting structure is used to carry the magnetic flux on which the machine depends for its operation.
  • the structure is laminated to reduce the effect of eddy currents, which flow in the steel due to the time rate of change of the flux.
  • machines with unvarying flux have unlaminated structures.
  • the field structure of a dc machine can be unlaminated (i.e. solid), though even in these machines a laminated structure is sometimes adopted in order to improve the transient response for a new operating condition.
  • the degree of lamination is usually determined by the frequency of flux variation in the machine.
  • a lamination thickness of 0.50 or 0.65mm is often adopted.
  • a lamination thickness of 0.20mm is typical.
  • the output of the machine is also dependent on the so-called magnetising characteristic of the steel used.
  • This is the relationship between the magnetising effort applied to the steel (i.e. the magneto motive force, mmf) and the flux consequently produced.
  • mmf magneto motive force
  • the invention provides, in one embodiment, a stator for an electrical machine, comprising a core defining at least one stator pole having end faces, and at least one coil embracing the at least one stator pole, a surface of the coil and at least one of the end faces defining a space, the stator further comprising a magnetisable flux plate having a projecting portion at least partially occupying the space.
  • the projecting portion has a lateral profile generally conforming to the profile of the pole. This maximises the flux carrying capability of the flux plate.
  • a solid flux plate can be formed to fill the space.
  • the flux plate can be made of laminations which generally conform to the shape of the space. The thickness of the projecting portion of the flux plate is usually influenced by the bend radius of the coil around the pole end face.
  • the flux plate may have a profile that is the same as that of the stator core.
  • the edge of the profile of the flux plate may define an outer margin at the end of the core at least in the region of the pole sides or be coincident with the end of the core.
  • the core may comprise laminations which each define the profile of the stator, the flux plate being thicker than the laminations of the core.
  • the laminations are made of magnetisable steel, as referred to above.
  • the flux plate is usually between 3 and 10 times the thickness of a lamination depending on the space to be filled.
  • assembly comprises a stator as defined and a movable member comprising laminations and a further or alternative flux plate having a similar profile to that of the member.
  • the profile of the flux plate may be undersized with respect to some or all of the corresponding profile of the lamination, thereby defining an outer margin at the edge of the core.
  • the machine is a rotary machine (for example a variable reluctance machine), but other embodiments may take the form of a linear machine.
  • the cores may be made up of radial laminations, the flux plate being axially thicker than the laminations of either core.
  • Embodiments of the invention include an electrical machine assembly comprising a movable member (e.g. a rotor) and a stator as defined.
  • a movable member e.g. a rotor
  • the flux plate of the movable member and/or the stator can be arranged, in use, to carry flux alongside (i.e. geometrically generally parallel to) the flux path through the stator core and the movable member.
  • the invention is a method of increasing the flux carrying capacity of an electrical machine which comprises a stator made of laminations of magnetisable material of a first thickness, and a rotor made of laminations of magnetisable material of a second thickness, the method comprising: arranging at least one magnetisable flux plate against the laminations of one or both of the stator and rotor, which flux plate has a profile which is similar to the lamination against which it is arranged, and has a thickness which is greater than that of the lamination, the flux plate being arranged to carry flux alongside the flux path through the rotor and stator.
  • the stator comprises a core defining at least one stator pole having end faces, and at least one coil embracing the at least one stator pole, the method further comprising at least partially occupying a space between a surface of the coil and at least one of the end faces with a projecting portion of the flux plate.
  • the flux plates are arranged adjacent laminations of the stator and rotor, the method further comprising aligning the flux plates so that the flux carried by the flux plates is in parallel with the flux through the rotor and stator.
  • the flux plates are arranged adjacent laminations of the stator and rotor, the method further comprising arranging one of the flux plates to overlap the other.
  • Figure 5 shows a stator flux plate which is shaped to co-operate with the end of a stator core pack having a stator back-iron portion, and poles having pole sides and pole ends, as shown in Figure 3, for example.
  • a solid flux plate 50 has an annular portion 51, whose inside and outside diameters correspond to the back-iron portion of the stator lamination.
  • a number of teeth 52 project radially inwardly from the annular portion. Each tooth 52 has dimensions which allow the tooth to match the shape of the stator poles 44, or to lie slightly inside the profile of the pole. The number of teeth on the flux plate is the same as the number of stator poles.
  • the cross section of the plate shows it has a flat side 53 which lies adjacent the end face of the stack of magnetisable laminations making up the stator core 42.
  • the opposite side 54 of the plate is profiled at the teeth to match the profile of the gap 47 (see Figure 3) created between the coil overhang 46 and the pole end.
  • Figure 5 shows a flux plate 50 with twelve teeth, suitable for use with the twelve-pole stator 61 shown in Figure 6.
  • the shape of the flux plate 50 is the same as the shape of the axial profile of the stator core.
  • the profile of the flux plate may be generally slightly less so that the difference between the two profiles defines a margin.
  • the margin may be between 0.1mm and 0.7mm, for example 0.5mm.
  • Figure 6 shows an exploded schematic of an electrical machine with a stator core 61 having two flux plates 50.
  • the plates 50 are fitted to the ends of the core 61 before the coils 49 are assembled to or wound on the core, so that the teeth 52 of each flux plate are encircled by the overhangs of the coils.
  • the flat face 53 of each flux plate is arranged against the end of the core.
  • each flux plate is made of unlaminated ferromagnetic material. Each is continuous across its radial profile. The material is chosen for its flux-carrying qualities and for its suitability to be machined, cast, stamped or forged with the appropriate profile on the teeth, rather than for any qualities of mechanical strength. A suitable material for some applications is steel type EN9.
  • Figure 7 shows a corresponding rotor flux plate 71, which has a number of teeth 72 corresponding to the number of poles on the rotor 45. Since the rotor carries no winding in this example, the outer surface of the teeth 72 need not be profiled across their width, but can have a rectangular form. This is simpler to manufacture than the profiled teeth of the stator flux plate 50.
  • the rotor flux plate 71 is assembled to one or both ends of the rotor core pack 60, so that its position aligns axially with the corresponding stator flux plate.
  • the material for the rotor flux plates is chosen according to the criteria also used for the stator flux plates, with the additional criterion that the material also requires sufficient mechanical strength to withstand centrifugal forces developed when the machine is operating.
  • the axial profile of the rotor flux plate may be defined to the same as the profile of the rotor lamination itself.
  • the equivalent margin between profiles as described in relation to the stator may be defined in the region of the rotor poles or throughout.
  • the rotor flux plate is continuous across its profile.
  • the rotor flux plate can be formed with a circular axial recess which will provide clearance for a rotor bearing on the rotor shaft and/or a bearing housing on the fixed member.
  • this invention finds particular application in motors for confined spaces in which the flux carrying capacity of the machine for a given size has to be enhanced as much as possible.
  • it can be advantageous to sacrifice a certain amount of flux carrying capacity in the flux plate for the sake of mechanical compactness by providing clearance for the rotor and/or its housing.
  • the presence of the flux plate(s) presents one or more paths for the flux alongside and generally parallel to the main flux path of the stator and rotor, thus reducing the reluctance of the magnetic circuit and reducing the current required to support a given level of flux, thereby enhancing performance of the machine.
  • the flux plates effectively form part of the main magnetic circuit, taking advantage of the otherwise unused axial space between the winding overhangs and the pole ends.
  • the amount of flux flowing in the flux plate(s) will depend on the frequency of excitation. At zero frequency, the amount of flux in the plates is a maximum, but as the frequency rises eddy currents in the plates will gradually reduce the flux, so that, at the higher frequencies used for operation at high speeds, the plates effectively carry no flux.
  • FIG. 6 shows an arrangement with one rotor flux plate 64 and two stator plates 50. Equally possibly, the assembly could have two rotor flux plates and one or two stator flux plates.
  • Figure 8 shows a motor, similar to that shown in Figure 3, fitted with stator flux plates 82, 84 and a rotor flux plate 85.
  • the lower view shows that the stator flux plates are adjacent the axial ends of the stator 42 and virtually fill the gaps in the axial direction under the coil overhang 46 embracing a pole.
  • the section A-A shows that, in this example, the stator flux plates 82, 84 define a margin 86/87 with respect to both the inner and outer profiles of the stator core, while the rotor flux plate only has a margin 88 with respect to the rotor core at the pole faces.
  • stator flux plate can be manufactured as a simple stamping from a flat plate. Although this simplifies manufacturing, it prevents the stator flux plate mating closely with the profile of the winding and therefore does not optimise the use of the space.
  • shape of each tooth of the stator flux plate can be arranged with a rectangular shape. This would extend across the width of the pole but not outwardly fully into the axial extent of the overhang.
  • a further variant is to make the flux plate from a series of stampings, each of which is a sector of the full plate.
  • the gap between the adjacent stampings should preferably be controlled so that it is smaller than the main airgap length between the teeth of the rotor and stator flux plates.
  • One further alternative embodiment of the invention has a stator flux plate whose teeth extend radially past the main working airgap of the machine.
  • the teeth of the stator flux plate at one end of the core are, thus, extended so that an axial component of the flux path is defined from the tooth on the stator flux plate into the tooth on the rotor flux plate. This leads to a torque produced by the axial flux component.
  • Flux from the stator flux plate passes axially into the rotor flux plate. This is illustrated in Figure 9, which shows a partial cross-section of a machine.
  • the laminated rotor core 91 is mounted on a shaft 92 and has a flux plate 94.
  • the laminated stator core 90 has a flux plate 93 which extends radially beyond the flux plate 94 so that one flux plate radially overlaps the other.
  • the broken line 95 shows schematically the flux path alongside that of the stator and rotor, passing radially down the stator flux plate, axially across a small gap separating the flux plates and then radially down the rotor flux plate.
  • stator flux plate An additional benefit of the stator flux plate is that the radial projections extending inside the coil overhangs provide heat paths from the inner face of the end of the coil to the stator outer diameter. This provides a means of improving the cooling of electric machines which are cooled by extracting heat from the outer diameter.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)
  • Synchronous Machinery (AREA)
EP05250787A 2004-02-16 2005-02-11 Magnetkreise für elektrische Maschinen Withdrawn EP1564872A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0403395 2004-02-16
GBGB0403395.7A GB0403395D0 (en) 2004-02-16 2004-02-16 Magnetic circuits of electrical machines

Publications (1)

Publication Number Publication Date
EP1564872A2 true EP1564872A2 (de) 2005-08-17

Family

ID=32011980

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05250787A Withdrawn EP1564872A2 (de) 2004-02-16 2005-02-11 Magnetkreise für elektrische Maschinen

Country Status (5)

Country Link
US (1) US20050212371A1 (de)
EP (1) EP1564872A2 (de)
KR (1) KR20050081873A (de)
CN (1) CN1658473A (de)
GB (1) GB0403395D0 (de)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20080026872A (ko) * 2006-09-21 2008-03-26 엘지전자 주식회사 스위치드 릴럭턴스 모터
TWI695447B (zh) 2013-11-13 2020-06-01 布魯克斯自動機械公司 運送設備
TWI742414B (zh) * 2013-11-13 2021-10-11 美商布魯克斯自動機械公司 密封切換的磁阻馬達
KR102665385B1 (ko) * 2013-11-13 2024-05-13 브룩스 오토메이션 인코퍼레이티드 밀봉된 스위치드 릴럭턴스 모터
US9948155B2 (en) 2013-11-13 2018-04-17 Brooks Automation, Inc. Sealed robot drive
KR20220000416A (ko) 2013-11-13 2022-01-03 브룩스 오토메이션 인코퍼레이티드 브러쉬리스 전기 기계 제어 방법 및 장치
KR101597966B1 (ko) * 2014-07-31 2016-02-29 전자부품연구원 횡방향 공극이 추가된 영구자석형 동기 전동기
CN107872133B (zh) * 2016-09-23 2019-07-05 徐夫子 机械换相式磁阻发电机
CN112787432B (zh) * 2019-11-01 2022-10-11 上海海立电器有限公司 一种内置式保护器的基座结构

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59194652A (ja) * 1983-04-20 1984-11-05 Fanuc Ltd 永久磁石同期電動機の回転子
US4585967A (en) * 1983-10-21 1986-04-29 General Electric Company Rotor of AC dynamoelectric machine with improved cooling and stability and method of making the same
US5140211A (en) * 1987-09-17 1992-08-18 Fanuc Ltd. Rotor structure of a synchronous motor
US5563463A (en) * 1988-06-08 1996-10-08 General Electric Company Permanent magnet rotor
US5006748A (en) * 1989-08-17 1991-04-09 Rem Technologies, Inc. Stator mounting arrangement
US5176946A (en) * 1991-05-10 1993-01-05 Allen-Bradley Company, Inc. Laminated contactor core with blind hole
GB2258765B (en) * 1991-06-27 1996-01-10 Dana Corp Variable reluctance motor having foil wire wound coils
US5719456A (en) * 1994-05-18 1998-02-17 Dana Corporation Variable reluctance electric motor
US6025668A (en) * 1995-12-08 2000-02-15 Dana Corporation Variable reluctance motor having bifurcated stator poles
GB2310544B (en) * 1996-02-21 2000-03-29 Switched Reluctance Drives Ltd Method of forming a rotor for a reluctance machine
EP0884825B1 (de) * 1997-05-14 2003-12-17 Toyota Jidosha Kabushiki Kaisha Stator für einen Elektromotor
US6772503B1 (en) * 2000-08-22 2004-08-10 Honeywell International Inc. Rotor assembly having bonded lamination stack
US6069431A (en) * 1998-02-06 2000-05-30 Isuzu Ceramics Research Institute Co., Ltd. Synchronous generator
EP2276146A1 (de) * 1999-07-16 2011-01-19 Panasonic Corporation Synchronmotor mit Dauermagneten
EP1241773B1 (de) * 2001-03-14 2012-09-12 Nissan Motor Co., Ltd. Drehende elektrische Maschine mit Spalttopf
US6868738B2 (en) * 2002-07-31 2005-03-22 Troxler Electronic Laboratories, Inc. Method and apparatus for determining the angle of gyration and/or the pressure in a gyratory compactor

Also Published As

Publication number Publication date
US20050212371A1 (en) 2005-09-29
KR20050081873A (ko) 2005-08-19
GB0403395D0 (en) 2004-03-17
CN1658473A (zh) 2005-08-24

Similar Documents

Publication Publication Date Title
US8169109B2 (en) Electrical machine with dual radial airgaps
US6064132A (en) Armature structure of a radial rib winding type rotating electric machine
EP1564872A2 (de) Magnetkreise für elektrische Maschinen
AU2004247246B2 (en) Radial airgap, transverse flux motor
US6940198B2 (en) Brushless permanent magnet machine with reduced cogging and torque ripple and method of producing the same
US7307366B2 (en) Brushless permanent magnet machine with axial modules of rotor magnetization skew and method of producing the same
Li et al. Modification in rotor pole geometry of mutually coupled switched reluctance machine for torque ripple mitigating
US6211595B1 (en) Armature structure of toroidal winding type rotating electric machine
US20040251761A1 (en) Radial airgap, transverse flux motor
US20080246362A1 (en) Radial airgap, transverse flux machine
EP1359660B1 (de) Geschalteter Reluktanzmotor
US7247964B2 (en) Electrical machine with magnetized rotor
US10749385B2 (en) Dual magnetic phase material rings for AC electric machines
EP1764897B1 (de) Rotor für eine elektrische Reluktanzmaschine
US6181041B1 (en) Inductance rotating electric machine
US20040090134A1 (en) Generator having a brushless excitor and power generating installation making use of the same
Hieu et al. Design and control of a high speed segmental stator 4/3 switched reluctane motor
Washington et al. Methods for the construction of single-sided axial flux machines using soft magnetic composites
JP2007166798A (ja) 回転電機、圧縮機、送風機、及び空気調和機
Lu et al. Performance investigation of odd primary pole linear switched-flux PM machine with mechanical flux adjuster
He Ultra-high-speed Three-phase Permanent Magnet Motors
Moury et al. A new approach to minimize the cogging torque of axial flux PMG for under water applications

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU MC NL PL PT RO SE SI SK TR

AX Request for extension of the european patent

Extension state: AL BA HR LV MK YU

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Effective date: 20081022